1. Technical Field
The invention relates to a zwitterionic monomer, a polyzwitterion synthesized from the zwitterionic monomer, a pH-responsive polyzwitterionic acid synthesized from the polyzwitterion, a polyzwitterion/anion and polyzwitterion/dianon synthesized from the polyzwitterionic acid, and the corresponding methods by which each compound and polymer is formed and use of the polyzwitterionic acid as an antiscalant.
2. Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
The polymers conventionally used in water-base fluids are acrylamide derivatives, generally acrylamide/acrylate copolymers obtained by copolymerization of acrylamide and acrylate or by polyacrylamide hydrolysis. They are however sensitive to the conditions of use that can be encountered. A high shear gradient and/or a high bottomhole temperature can lead to a decrease in molar mass and viscosifying power. Furthermore, they are sensitive to media with high ionic strength because of the presence of carboxylate or sulfonate groups which also lead to a loss of viscosifying power or even to a precipitation in media with high divalent ion concentrations.
For applications in saline media, polyampholytes carrying both positive charges and negative charges can be suitable. When the charges on the polymeric material are in equal number (neutral polyampholytes) and proton exchange is suppressed, the properties in aqueous solution of these materials are governed by the attractive forces that exist between the unlike charges of the polyampholyte. They are generally more soluble and have higher viscosities in a saline medium than in deionized water. The behaviour of this type of polymer is therefore referred to as antipolyelectrolyte behaviour.
In the case of polyampholytes that do not have the same number of positive and negative charges, according to the extent of the excess of one charge type in relation to the other, the polyelectrolyte effect or the neutral polyampholyte effect characterizes behaviour in solution.
These polyampholytes are already used in many applications, in particular for the formulation of cleaning compounds and cosmetic applications, the latter depending on the nature of the zwitterion, composition of the polymer and on the molar mass of the polymer.
Butler's cocyclopolymerization protocol (G. B. Butler, “Cyclopolymerization and cyclocopolymerization,” Marcel Dekker: New York, 1992; S. Kudaibergenov et al., Advances in Polymer Science, 2006, 201, 157-224; P. K. Singh, et al., e-Polymers, 2007, 030, 1-34; W. Jaeger, et al., “Prog. Polym. Sci.,” 2010, 35, 511-577—each incorporated herein by reference in its entirety) involving N,N-diallyl quaternary ammonium salts has generated a plethora of industrially significant water-soluble cationic polyelectrolytes. Use of ammonio monomers [(CH2═CH—CH2)2NH+R—Y−] having unquenched nitrogen valency and pendent (R) bearing carboxylate, phosphonate or sulfonate functionalities (Y−) have provided entries into polymers which can participate in pH-induced equilibrations involving cationic (+), anionic (−), zwitterionic (±) and ampholytic (+−) centers in the repeating units (H. A. Al-Muallem, et al., Polymer, 2002, 43, 4285-4295; S. A. Ali, et al., J. Polym. Sci. Part A: Polym. Chem, 2003, 41, 172-184; O. C. S. Al-Hamouz, et al., J. Polym. Sci. Part A Polym chem, 2012, 50, 3580-3591; N.Y. Abu-Thabit, et al., J. Appl. Polym. Sci., 2011, 120, 3662-3673—each incorporated herein by reference in its entirety). Bio-mimicking polyampholytes and polyzwitterions, have also offered many new applications in biotechnology, medicine, oil industry, and hydrometallurgy.
While the cationic or anionic polyelectrolytes demonstrate polyelectrolyte behavior, i.e. their viscosity is diminished upon addition of electrolytes (e.g. NaCl), the polyzwitterions (PZs) show anti-polyelectrolyte behavior of enhanced viscosity and solubility as a result of globule-to-coil transition. The transition is an outcome of salt-induced disruption of intragroup, intrachain and interchain ionic cross-links (J. C. Salamone, et al., Polymer, 1978; 19, 1157-1162; T. A. Wielema, et al., Eur. Polym. J., 1987, 23, 947-950; P. G. Higgs, et al., J. Chem. Phys., 1991, 94, 1543-1554; M. Skouri, et al., Macromolecules, 1994, 27, 69-76—each incorporated herein by reference in its entirety).
Antiscalants are chemical substances that inhibit the formation of scales which is a nuisance in the operation of water desalination plants (R. J. Davey, The Role of Additives in Precipitation Processes, Industrial Crystallization 81, Eds. S. J. Jancic and E. J. de Jong, North-Holland Publishing Co., 1982, 123-135—incorporated herein by reference in its entirety). Calcium sulfate and calcium carbonate are primary contributors to scale formation. Scale deposits, which are generated and extended mainly by means of crystal growth, can be inhibited by modification of its growth and dispersion of the scale forming minerals. Various polyelectrolytes, which are usually added to saline water in substoichiometric amounts, are adsorbed onto the surfaces of the crystals so as to inhibit further crystal growth. A mixture of 90:10 copolymer of acrylic acid/(CH2═CH—CH2)2N+(Me)CH2CH2SO3− and 2-phosphono butane 1,2,4-tricarboxylic acid (PBTA) has been reported (D. W. Fong, et al., U.S. Pat. No. 6,225,430 B1, May, 2001—incorporated herein by reference in its entirety) to perform better scale inhibition than poly(acrylic acid) (PAA) alone or a mixture of PAA and PBTA.
When the monomer which represents repeating units of the polymer contains exactly one an ammonium group and a matching anionic group, it belongs to the betaine family and the charges form an inner salt. A distinctive feature of the polymers of the invention is that the unlike charges are of the betaine type and are thus electrically neutral polymers. The positive charge is provided by a quaternary ammonium function, the negative charge by a sulfonate (sulfobetaines) or phosphonate (phosphobetaines) group.
Some copolymers were obtained by copolymerization of acrylamide with carboxybetaine type monomers. Their properties in solution greatly depend on the pH value and they are incompatible with the desired properties. In fact, at a low pH value, the protonation of the carboxylate functions leads to the loss of the zwitterionic character and the copolymer behaves like a cationic polyelectrolyte, thus sensitive to the presence of salt in particular.
The polybetaines described here have the advantage of keeping their zwitterionic character within a wide pH range. Certain acrylaride and sulfobetaine copolymers have already been described, but they result from synthesis processes carried out in the presence of salts, which is of notable importance for the structures obtained.